Commentary: Better Questions to Answer

Salix is highly controversial because it is the only race-day medication allowed in North America.

Photo: Anne M. Eberhardt/The Horse

Eric Mitchell, editorial director and editor-in-chief of The Blood-Horse, shares his thoughts on Salix and possible studies on the drug.

No debate regarding the use of the anti-bleeding drug furosemide (known as Salix or formerly Lasix) is complete without a call for more research.

The Jockey Club pushed on this front during a recent meeting of the Kentucky Equine Drug Research Council (KEDRC), where it lobbied for a study to look at the effectiveness of Salix given at different time intervals prior to a race. The KEDRC advises the Kentucky Horse Racing Commission on medication policies and awards money for funding of medication studies.

Salix is highly controversial because it is the only race-day medication allowed in North America. Horses are permitted to get Salix at least four hours prior to a race as a preventative for exercise-induced pulmonary hemorrhage (EIPH), also known as bleeding. The drug is a diuretic, meaning it causes horses to urinate a lot and consequently drop significant amounts of body weight from the water loss. Studies have shown this weight loss can contribute to enhanced performance, which is why the medication is so controversial.

On the one hand, the medication is considered important in racehorse welfare because research has shown it reduces incidences of EIPH. Still, its use does influence performance and its long-term effects on racehorse health are unknown. Anecdotally, trainers have said horses given a regular regimen of Salix take longer to recover following races.

The Jockey Club’s proposal recommended studying the effectiveness of administering Salix 24 hours, 12 hours, six hours, or maybe even two hours out from a race. A formal proposal to this admittedly narrowly focused study has yet to been drafted.

KEDRC members Andy Roberts, DVM, a veterinarian representing the Kentucky Harness Horsemen’s Association, and Rick Hiles, president of the Kentucky Horsemen’s Benevolent & Protective Association, both don’t like the proposed study because The Jockey Club has already made it clear it wants U.S. medication rules on par with the rest of the racing world, which bans all race-day medication use. Roberts called the proposal “a ridiculously thinly veiled attempt to get rid of Lasix.”

Well, it would certainly be one way to address the race-day issue if a study showed that Salix could be given more than 24 hours out but let’s hope the current research push doesn’t stop there. A real issue with Salix is whether racehorses should routinely be given Salix at all. Two recent studies indicate maybe it should not.

A presentation given during the recent International Conference on Equine Exercise Physiology, held June 16-20 in the United Kingdom, showed evidence that a single dose of Salix caused a negative calcium balance in horses for 72 hours after it was administered. The study was done by Kentucky Equine Research, based in Versailles, Kentucky. Co-author and KER president Joe Pagan, DVM, said his research, done on six Thoroughbreds, signals the need to do a more robust study on the effects of Salix on mineral balance and soundness in racehorses.

Then, an Australian study published June 11 in The Veterinary Journal indicates a genetic component to epistaxis (bleeding from the nostrils), which is the most severe degree of EIPH where blood is observed in the nostrils and does negatively affect performance. Race records and reported occurrences of epistaxis in 117,088 racehorses entered in races or official barrier trials between Aug. 1, 2000, and Feb. 22, 2011, were analyzed by the team of Brandon Velie, Herman W. Raadsma, Claire M. Wade, P.K. Knight, and Natasha A. Hamilton. The researchers looked at both genetic and non-genetic factors that contribute to epistaxis.

“While this is only the second published study to estimate the heritability of epistaxis, it is worth noting that these estimates, along with those by Weideman et al. (2004), provide strong evidence to suggest an equal or greater genetic contribution to epistaxis compared to many racing performance traits,” the study states.

“It is possible that epistaxis requires specific (combinations of alleles at adjacent locations on a chromosome) that may increase the vulnerability of a horse to pulmonary capillary stress failure during exercise,” the study continued. “This genetic susceptibility would then most likely result in some horses being more sensitive to certain environmental triggers, potentially explaining the variation in significant non-genetic factors between populations.”

The authors raise the question about medication masking such a genetic trait but don’t go so far as to suggest horses genetically predisposed to epistaxis should not be breeding animals. They do note that such knowledge would be valuable to owners and trainers to “allow for modified management plan” to reduce incidences of epistaxis.

It’s understood small steps are required to gather good data. But the resources for quality research are precious, so let’s be sure to also push for studies that lead to substantive change.

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